You should be OK even if you get stopped for a routine traffic stop.
If you are driving to Michigan, why do you want to go through Chicago?
You can bypass the whole city (and miss a lot of crappy traffic) by taking I-80 to 90-94 and head up to Michigan that way. If you are heading to the UP use I-39 and head up through Rockford. If you want any routing info let me know where you are heading in Michigan.
Truth is, I'd be less worried about the Chicago cops stopping you because of bumper stickers and more concerned about tyhe traffic mess that keeps the downtown "spaghetti bowl" tied up day and night.
If your rifle is in a case and the ammunition is separate you should have no problem even if you are stopped. If your state requires an ID card have it in your wallet. In all my years living in Chicago (54) I've never had a cop ask if I have any weapons in the car when stopped for a traffic issue.
And yeah, I hate that we are one of the few states with no carry laws. As long as Daley has a stranglehold on the state and feels the honest people are just too stupid and unreliable to trust, we have a problem. Our best chance is a national law I think. We finally have a candidate for governor, O'Malley, that believes in concealed carry. Wish us luck.
Have a good trip.
Don P.